1. Field
The present aspect relates to a chargeable and dischargeable non-aqueous electrolyte secondary battery used mainly as a power source of mobile electronic equipment such as a video camera, a mobile computer, and a mobile telephone, and more specifically, to a battery pack in which a lithium-ion secondary battery or the like is accommodated in an insulating case.
2. Description of Related Art
In recent years, a chargeable and dischargeable rectangular parallelepiped non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery has been mainly used as a power source of rapidly proliferating mobile electronic equipment such as a video camera, a mobile computer, and a mobile telephone. The lithium-ion secondary battery has a structure in which an electrode assembly comprising a positive electrode and a negative electrode wound via a separator is accommodated in a rectangular parallelepiped case made of aluminum or an aluminum alloy.
A protecting circuit substrate that controls the battery voltage to prevent overcharge and over-discharge is disposed on one side surface of the lithium-ion secondary battery (unit cell) to form a battery assembly. The battery assembly is accommodated in an insulating case made of, for example, a synthetic resin to form a battery pack, and the battery pack is attached to electronic equipment. The protecting circuit substrate and the cell are electrically connected together by a lead plate for connection.
Japanese Patent Application Laid-Open No. 2005-190852 discloses a battery pack assembled by holding a cell in an upper case and a lower case each having the shape of a box with an opening on one surface thereof, which are prepared by splitting a case parallel to a flat surface portion of a battery assembly having the shape of a square flat plate into an upper part and a lower part, and then joining the cases by a method such as ultrasonic welding.
Japanese Patent Application Laid-Open No. 2005-100689 discloses a battery pack in which the undersurfaces of the upper case and the lower case are opened to form picture-frame-like upper and lower frames and after these frames are combined together, a label is wound.
Japanese Patent Application Laid-Open No. 2005-190956 discloses a battery pack in which the undersurface of the case is opened to form a picture-frame-like lower frame and after the lower frame is combined with the upper case, a label is wound.
Japanese Patent Application Laid-Open No. 2005-135770 discloses a battery pack in which an outer frame covering the side surfaces of the battery assembly is separated vertically to the plane surface of the battery assembly into U-shaped right and left frames and after these frames are fitted on the battery assembly, a label is wound. This patent application publication also discloses a battery pack in which the battery assembly is accommodated in a box-shaped case having an opening on one surface thereof and after a sheet cover is placed on the opened surface of the battery assembly, a label is wound.
Japanese Patent Application Laid-Open No. 2005-158452 discloses a battery pack in which a substrate accommodating part for accommodating a protecting circuit substrate is provided on a side plate of a rectangular frame where an external output terminal exposing window is provided.
Japanese Patent Application Laid-Open No. 2006-164559 discloses a battery pack having a case in which a rectangular frame surrounding the periphery of a battery assembly in which a protecting circuit substrate is disposed on one end surface of the cell is formed integrally with a rectangular plate covering the lower surface of the battery assembly, the frame on the side of the end surface serves as a coupling frame that causes the output terminal to be exposed, and the substrate accommodating part in which the protecting circuit substrate is fitted is provided on the coupling frame.
In the battery packs of Japanese Patent Application Laid-Opens Nos. 2005-190852, 2005-100689, 2005-190956, and 2005-135770, since a plurality of cases or frames are assembled or a box-shaped case and a sheet cover are combined together, the number of components is large and the structure is complicated. In addition, the number of assembly man-hours is large and the assembly process is complicated.
In the battery back of Japanese Patent Application Laid-Open No. 2005-135770, if the sheet cover is not accurately pasted to the battery assembly, it can occur that the sheet cover overlaps the side plate of the case or a large clearance is formed between the sheet cover and the case and this causes the inside of the battery pack to be exposed. For this reason, the sheet cover requires extremely high dimensional accuracy, and its pasting is cumbersome.
In the battery packs of Japanese Patent Application Laid-Opens Nos. 2005-158452 and 2006-164559, the substrate accommodating part is provided on the integrally formed outer frame or case in order to solve the problems of the battery packs of Japanese Patent Application Laid-Opens Nos. 2005-190852, 2005-100689, 2005-190956, and 2005-135770, and the number of assembly man-hours can be reduced. Although the outer frame or the case is normally formed by molding plastic with a specifically designed mold, the substrate accommodating part has a structure that cannot be taken out by opening the mold, that is, a so-called “undercut” structure, so that the mold structure for mold release is complicated and this increases the cost of the mold. In addition, since the degree of molding difficulty is high, the yields of components are poor.